refactor(linter/plugins): re-order visit function merging code

apps/oxlint/src-js/plugins/visitor.ts

@@ -526,6 +526,16 @@ export function resetCompiledVisitor(): void {
   activeNonLeafVisitorsCount = 0;
 }
 
+/**
+ * Merger that merges visit functions for an AST node type.
+ */
+type Merger = (...visitFns: VisitFn[]) => VisitFn;
+
+/**
+ * Merger that merges handler functions for a CFG event.
+ */
+type CfgMerger = (...visitFns: CfgVisitFn[]) => CfgVisitFn;
+
 // Array used by `mergeVisitFns` and `mergeCfgVisitFns` to store visit functions extracted from an array of `VisitProp`s.
 // This array is used ephemerally, so we re-use same array for each merge.
 const visitFns: (VisitFn | CfgVisitFn)[] = [];
@@ -599,7 +609,68 @@ function mergeVisitFns(visitProps: VisitProp[]): VisitFn {
   return mergedFn;
 }
 
-type Merger = (...visitFns: VisitFn[]) => VisitFn;
+/**
+ * Merge array of CFG visit functions into a single function, which calls each of input functions in turn.
+ *
+ * The difference between this function and `mergeVisitFns` is that this function is for CFG event handlers.
+ * Unlike all other visit functions, CFG event handlers are called with more than 1 argument.
+ * We keep this separate from `mergeVisitFns` because the merger functions use `...args` to pass all arguments,
+ * which is likely less performant than the simpler version which passes a single argument.
+ * AST node visitation is a lot more common than CFG event visitation, and we want to keep the common case fast.
+ *
+ * The array passed is cleared (length set to 0), so the array can be reused.
+ *
+ * The merged function is statically defined and does not contain a loop, to hopefully allow
+ * JS engine to heavily optimize it.
+ *
+ * `cfgMergers` contains pre-defined functions to merge up to 5 CFG visit functions.
+ * Merger functions for merging more than 5 visit functions are created dynamically on demand.
+ *
+ * @param visitProps - Array of `CfgVisitProp` objects
+ * @returns Function which calls all CFG visit functions in turn
+ */
+function mergeCfgVisitFns(visitProps: CfgVisitProp[]): CfgVisitFn {
+  const numVisitFns = visitProps.length;
+
+  debugAssert(numVisitFns > 0, "`visitProps` should have at least 1 element");
+
+  let mergedFn: CfgVisitFn;
+  if (numVisitFns === 1) {
+    // Only 1 visit function, so no need to merge
+    debugAssertIsNonNull(visitProps[0].fn);
+    mergedFn = visitProps[0].fn;
+  } else {
+    // No need to sort in order of specificity, because each rule can only have 1 handler for each CFG event
+
+    // Get or create merger for merging `numVisitFns` functions
+    while (cfgMergers.length <= numVisitFns) {
+      cfgMergers.push(null);
+    }
+
+    let merger = cfgMergers[numVisitFns];
+    if (merger === null) merger = cfgMergers[numVisitFns] = createMerger(numVisitFns, true);
+
+    // Merge functions.
+    // Reuse a temporary array to avoid creating a new array for each merge.
+    // TODO: Make merger functions take an array of `VisitProp`s to avoid this operation?
+    typeAssertIs<CfgVisitFn[]>(visitFns);
+    debugAssert(visitFns.length === 0, "`visitFns` should be empty");
+
+    for (let i = 0; i < numVisitFns; i++) {
+      debugAssertIsNonNull(visitProps[i].fn);
+      visitFns.push(visitProps[i].fn!);
+    }
+
+    mergedFn = merger(...visitFns);
+
+    visitFns.length = 0;
+  }
+
+  // Empty `visitProps` array, so it can be reused
+  visitProps.length = 0;
+
+  return mergedFn;
+}
 
 /**
  * Create a merger function that merges `fnCount` functions.
@@ -674,70 +745,6 @@ const mergers: (Merger | null)[] = [
     },
 ];
 
-/**
- * Merge array of CFG visit functions into a single function, which calls each of input functions in turn.
- *
- * The difference between this function and `mergeVisitFns` is that this function is for CFG event handlers.
- * Unlike all other visit functions, CFG event handlers are called with more than 1 argument.
- * We keep this separate from `mergeVisitFns` because the merger functions use `...args` to pass all arguments,
- * which is likely less performant than the simpler version which passes a single argument.
- * AST node visitation is a lot more common than CFG event visitation, and we want to keep the common case fast.
- *
- * The array passed is cleared (length set to 0), so the array can be reused.
- *
- * The merged function is statically defined and does not contain a loop, to hopefully allow
- * JS engine to heavily optimize it.
- *
- * `cfgMergers` contains pre-defined functions to merge up to 5 CFG visit functions.
- * Merger functions for merging more than 5 visit functions are created dynamically on demand.
- *
- * @param visitProps - Array of `VisitProp` objects
- * @returns Function which calls all CFG visit functions in turn
- */
-function mergeCfgVisitFns(visitProps: CfgVisitProp[]): CfgVisitFn {
-  const numVisitFns = visitProps.length;
-
-  debugAssert(numVisitFns > 0, "`visitProps` should have at least 1 element");
-
-  let mergedFn: CfgVisitFn;
-  if (numVisitFns === 1) {
-    // Only 1 visit function, so no need to merge
-    debugAssertIsNonNull(visitProps[0].fn);
-    mergedFn = visitProps[0].fn;
-  } else {
-    // No need to sort in order of specificity, because each rule can only have 1 handler for each CFG event
-
-    // Get or create merger for merging `numVisitFns` functions
-    while (cfgMergers.length <= numVisitFns) {
-      cfgMergers.push(null);
-    }
-
-    let merger = cfgMergers[numVisitFns];
-    if (merger === null) merger = cfgMergers[numVisitFns] = createMerger(numVisitFns, true);
-
-    // Merge functions.
-    // Reuse a temporary array to avoid creating a new array for each merge.
-    // TODO: Make merger functions take an array of `VisitProp`s to avoid this operation?
-    typeAssertIs<CfgVisitFn[]>(visitFns);
-    debugAssert(visitFns.length === 0, "`visitFns` should be empty");
-
-    for (let i = 0; i < numVisitFns; i++) {
-      debugAssertIsNonNull(visitProps[i].fn);
-      visitFns.push(visitProps[i].fn!);
-    }
-    mergedFn = merger(...visitFns);
-
-    visitFns.length = 0;
-  }
-
-  // Empty `visitProps` array, so it can be reused
-  visitProps.length = 0;
-
-  return mergedFn;
-}
-
-type CfgMerger = (...visitFns: CfgVisitFn[]) => CfgVisitFn;
-
 // Pre-defined CFG mergers for merging up to 5 functions
 const cfgMergers: (CfgMerger | null)[] = [
   null, // No merger for 0 functions